Can I get pregnant from unprotected sex three days before ovulation and the day after using withdrawal method?

Sometimes yes. A woman who does not want to get pregnant can consider doing one or more of the following: stop having unprotected sex, stop having vaginal sex, buy Plan B if there was unprotected sex in the past 3 days, ask her doctor about getting an IUD placed if not already pregnant, ask her doctor for a prescription of Ella (ulipristal acetate) if there was unprotected sex in the past few days, etc...